Acrylonitrile polymerization process



aired States Patent PdLYMERIZA'E'EQN PIRDCESS Raymond Tietz, Wilmington, Del nssignor. to E. ii-

dn font; de Nemours and Company, Wilmington, Del.,

ice

the improved utilization of polymerizable unsaturated sulfonic acids and their salts in copolymerization reactions of monomer mixtures containing at least 85% acryloa corporation of Delaware nitrile.

Nam-Brewing. Filed Nov. 4, 1957,.Ser. No. 694,109 The ObJCtlVBS of this nvention are attained by coa Claims. (Cl. 260-795) polymerizing with free radical type initiators amixture e "a F v of addition polymerizable monomers comprising an etli gi gf sg z zziz? 2; ylenically unsaturated sulfonic acid or its salt in an speaifi ally this invention relates to the improved com amount equal v 9 3% of the total polymemtmn polymerization of 'a'orylonitrile and acidic monomers. mlxmre a-crylomvmie m an {amount equal m Yams from polyacrylonitme have poor affinity for 85 of the total monomerweight and other ethyiemcaliy dyes, and they can be dyed only with difiiculty using basic, gi momma? a: i g diluent acid and dispersed acetate-type dyes. Even then, how- 16 cc r; 9 0 e ggi ggt an ever, such dyeings are not entirely satisfactory. Deep iii g g ggg gg fi i ?g$ gg g d ein with basic d es is articularl desirable in order to n f cilitite crossand unio r i-dyeing (if yarns formed from i pasts and perce'magcs are'by wglght'unl'ess. acrylonitrile polymer fibers and wool (using acid dyes on 0t mdlcate Y wool) and with rayon (using direct dyes on the rayon). 2 1 EXAMPLE I one method sr t Pdymers with 0 Batch copoiymerizations of acrylonitrile (40% 'of entire good has: Y mvolves mclusmn in the Polymer system) and sodium allylsulfonate are carried out in 500 of 40 to 90 mllliequivalents of combined sulfur as sulfonic m1 3 flasks fitted with a reflux condenser a stirrer g i g g. p if grmgps Per klilogramf'yof and a nitrogen inlet. to maintain the polymerizatiori uc eantrssown coo mer ac o't' containing froin about 0 4 gei ceni to 3 r c ent 2 f a l y under a? atmosphere AP amount of aanwblslsomerizable sulfonic acid 6r its Salt W butyronitnle' n an amount equivalent to 0.2% of the total Copolyrners of acrylonitrile and such monomers as motiontl-er m thg-folymertlzauondls used a poly a me aionimlat a c n allylsulfomc acid and methallylsulfomc acid are known of i allytlsuignate z g i g z m g%gi but their. re aration is wasteful and ex nsive.- In conventional aq eous polymerizations the monomer rnix-' g i g a constant mg fi a i ture must contain at least 5 percent of suchan acidic ciem ggggi g gi g i g: g f gj ggg g f monomer to obtain c l o t 1 1 r of-the sulfonated mo no i- 'iu: 1 112 21153 il tifiii i i poi-ymegzauon reacugnhpmduct-mlxmgg r V tion'of the sulfonic acid (SA) in the polymerization reg gg i Qf axi g; $3222 1: 2: iri iii iieinciaction is only about 0.4 or lower (SA in copolymer/SA After flu d 1 1 t d in total monomer feed==0.4). t g 22? 3 ymer ISYWICG- gsqgpcn m Such poor relative utilizations of these acidic monogifi f z th Z ii i ggg r one? mers have heretofore precluded their commercial use in oven 3 c 1 e m vacuum copolymers of acrylonitrile, since these materials are expensive and their commercial use would require costly Q Q i t (desgnated D I) apparatus for recovery purposes. Also, the very low the P Y O System aeryl i relative utilization of an acidic monomer in comparison f H" s techniques at The m with the comonomers renders the oopolymer composiill/Q uillllfluon TBPFeFeHiS Weight of thfi q m 'tion very sensitive to the over-all conversion and involves sodlumanpylsulfoflate In the P Y Q formed y expensive and difiicult control measures to produce a '45 the sodium allylsulfonate present inthe initial monomer uniform copolymer. mixture, expressed as percent. 1

T able I soilil'rlrfm Atllyl Polymer CH8 6 I Run Polymerization Media Dielectric Relative Yield, (11.); Y Constant Utilization Percent Percent Percentoi Percent 'AcidltyvoiFeed Monomer SAS 5 1 water 70 0.1a 0. 32 0.020 1.0 0.08 3.4 4.3 0 do 0.25 0.03 0.043 an 0.07 4.4 4.9 2 a a a it 5 Bide water 00700 40 0. '12 0150 0100 40 1103 7L1 210 e (in 0.2; 0.00 0.84 08 1.40 8.0 1.0 7 dn 0.48 1.21 1.36 04 1.14 5.0 1.0 s 9-3; as as as a 10 -iiiZIF water 10 40-0 0125 0103 0.1 40 1111 3Z2 21g 11. DMF/water 50 50 54.8 0. 20 0. 05 0. 5a 87 0.81 8.4 as 12 Butyrolactone/wnter 80/20 59 0. 25 0. 63 0. 59 41 0. 94 6. 3 2. 9 13 Dlmethylsultoxide/wuter10/30 0.25 0.63 0.60 42 0. 91 28.1 as 1% g i t tli la cet y lge wmr 80/20 2 3.5g 1 .2g r g g 1. g; 11.2 1.0 W8 9 10 Ethylene Cairbonate/water 00/10... 0.25 0.63 0. 40 34 5 1']. Methyl Ethyl Ketouelwater /20. 60 02? 0.25 0.63 0.48 33- 0.70 4.2 1.0

l Dielectric constant of polymerization system. .I Mllllnqnlvalents per kilogram.

8 Dlruethylformamide.

t Tetremethylenesultone.

1 Sodium allyl suliouate.

prepared using the technique of Example I with several polymerization media as shown in. Table IV. The desalt elf allylsulfonic acid is used in place oi; the

aliylsulfonnte above.

EXAMPLE II Elie copolymerlza'ticn procedure of Example I is followed with the replacement of the sodium allylsulfonate with potassium cthylenesulfonate. The results areshown Table II. Molecular weights of the polymers formed as measured by inherent viscosity [11] are similar to those of Example I.

Table Ii Acidic Monomer Dielectric Bun Polymerization Media Constant Percent Relative Utilize.

$ 2 2 weooeoro 30/70 131. gmo 80/20 "PM unto--." 80/20 1 Butyrolactone. 8 Tetramethylenesulfone. 5 of polymerization system.

Similar results are obtained-when the sodium salt of ethylenesulfonic acid is used in place of the potassium salt.

EXAMPLE HI Copolym'crization of acrylonitrile and methallylsulfonlo acid is effected by the technique of Example I. The results with varying polymerization'media are shown in Table III. In run 28, the sodium salt of the free acid is used. A similar high relative utilization as compared with run 27 is seen. This monomer gives higher "relative, utilization values than other acid monomers, but the improvement with a system of low dielectric constant in apparent.

Similar results are obtained when acrylonitrile is replaced with a 94/6 mixture of acrylonitrile and methyl acrylate.

The substitution of sodium methallyldisulfonate (sodium-Z-methyl propene 1,3-disulfonate) for methallylsul-v ionic gives similar results.

' EXAMPLE IV carom of acrylonitrile and aliylsulicnic acid are pendency of relative utilization" are given level of acidic monomer present inthe, total monomer mixture upon the dielectric constant of the polymerization system is clearly shown.

raw; 1v

- Acidic Monomer j Dielcc- I Run Polymerization Media tz'i'c Con- Percent Relative stunt I 0t other Utiliza- Montion omers ao-- DMF 39 0.25 as 31..... MF 39 0.40 2.0 32 DMF/il O /20 46.4 0.27 1.0 33---... DMFll-hO 60/50 54.8 0.27 1.0 34-..-.- DMF/FlzO 30/70 0.25 v 0.7 35..-- F/CQH 30 70 19.4 0.41 3. 7 30"..- DMF/Methyl Ethyl 30/70 20.4 0.41 3. 4

Ke no.

I For DMF alone. I 01' polymerization system.

EXAMPLE V Although this invention has been illustrated bymeans of batch polymerizations in order to more clearly show the advance made, it has its greatest utility in the realm of continuous polymerization reactions, as shown in this I example. A mixture of monomers (acrylonitrile/methyl acrylate (9.3/7)) in the amount of 55 parts is added continuously, along with 45 parts dimethylformamide/ water (85/15); triethylammonium ethylenesulfonate in the amount of 0.45% based on the other monomers (and calculated as' the acid); benzoyl peroxide in the amount of 0.20% based on monomers; triethylamine in the amount of 0.07% based on monomers; sulfurdioao ide in the amount of 0.13% based on monomers; and

ferrous ion in the amount of 10p.p.m. based on monomars; through appropriate metering devices to a waterjacketed, stirred aluminum reactor under-a blanket of nitrogen gas at such a rate that the contents of the re actor. are completely replaced every minutes. 'ilcle temperature is maintained at 55 C. and the slurry containing polymer and unreacted monomer and diluent is continuously caught and shortstopped against further polymerization by the addition of 0.06% thiourea based on the monomers and 0.20% triethylamine based on the monomers. Timed samples of the polymer slurry are collected, the polymcr'completely precipitated, washed and dried. Conversion of monomers to copolymer is 49% and inherent viscosity of the copolymeris 1.3. The resulting copolymer contains 0.49% ethylenesulfonic acid units after corrections are made for acidic end groups derived from the sulfur dioxide. Thus, a relative utilization of 1.1 with the sulfonated monomer is obtained.

The copolymer is converted into a solution suitable for spinning by evaporation of excess unrcacted monomers and removal of water under a vacuum of 100 mm. mercury pressure (absolute) until a solution of 25-30% solids has been formed. This solution is extruded at 100 C. through a spinneret containing 5 orifices. each 0.0065 inch in diameter, into an inert gas at C. and the resulting filaments wound up at 100 yards per minute. After extracting the residual dimethylformamide with water at 100 C., the yarn is drawn to 4 times its original.

length in 95 C. water. The resulting strong yarn has an the examples, is defined as lnNr wherein c is the concentration of the polymer in 100 ml. of the solvent and Nr is the symbol for relative viscosity (the ratio of the. tlow time of thepolymer solution relative to the How time of the solvent). The viscosity meas- 'urements are made on V2% solutions of the polymer in v dimet-hylformamide (DMF) at 30 C.

By the expression polymerization system" is meant the mixture of monomers other than the sultonic acid compound, solvent for the polymer and/or a liquid diluent that is a non-solvent for the polymer.

The acidity of the polymer is determined by percolating a dimethylformamide solution of the polymer through an ion exchange column containing a mixture of a strongly, acidic resin and'a strongly basic resin followed by passage through a column containing the acidic resin alone. The free acid groups in the polymer solution were then titrated using an alcoholic solution of KOH and a suitable indicator. The polymer concentration was determined by evaporating a portion of the solution-to dryness. Analytical results were expressed as milliequivalents of acidic groups per kilogram of dry polymer.

The process of this invention has been illustrated with the copolymer-ization of acrylonitrile with monomers containing sulfonate groups and with a third monomer, methyl acrylate. In addition to acrylonitrile and unsaturated sulfonic acids or their salts, other monomers copolyinerizable with acrylonitrile as disclosed in us. 2,456,360 to Arnold and US. 2,436,926 to Jacobson can be used as the third or fourth monomer present in amounts up to about 14% of the total monomer concentration. Best results in terms of fiberphysical properties are Obtained when the acrylonitrile content is kept above 90% with no more than about 9% of all other monomers being used.

In addition to allylsulfonic acid, methallylsulfonic acid, ethylenesulfonic acid and methallyldisulfonic acid and their salts, other ethylenically unsaturated sulfonic acids such as those disclosed in US. 2,601,256 to Bruson and US. 2,527,300 to Dudley may be used. These sulfonated monomers may be used in the acid form but are preferably used in the form of their salts, such as the ammonium, substituted ammonium (e.g., triethyl ammonium), and metal salts (e.g., sodium, potassium, lithium, zinc, magnesium, calcium, etc.).

The sulfonated monomers of this invention are used in amounts from 0.1% to 3.0% of the total polymerization mixture and preferably from 0.2% to 2.0% depending on their molecular weight and the number of sulfonate groups they contain. Higher concentrations drastically reduce the relative utilization of these monomers.

The liquid media or diluent for the polymerizations of this invention may be any inorganic or organic liquid having a dielectric constant of 60 or less. Preferably,

. such media which may consist of a single compound or a mixture should be chemically inactive towards all the components of the polymerization mixture. A preferred composition utilizes a solvent for the polymer in the pure form or diluted with other substances, such as water, benzene, methyl ethyl ketone, to name a few. The use of a solvent for the polymer formed is of special advan ylncetamide, diluted or undiluted, afford surprisingly superior relative utilization? of the acidic monomers and are preferred solvents in the process'of this invention.

Any suitable acrylonitrile polymerization initiation sys' tem can be used. These arewell known in the Diaroyl peroxides, diacyl peroxides, organic azo com pounds as disclosed in U.S. Patent 2,471,959, perdisulfuric acid and its salts, hydrogen peroxide, and 'acyl and aroyl peracids are especially suitable.

Peroxides of the structure RCO--O O--COCR where R is alkyl or aroyl (ie., diacyl or diaroyl peroxides) are especially suitable for use in the process of this invention. They may be thermally decomposed, but, for sake ofthe easier control (being less temperature sensitive) and bet ter color. in the polymer, a redox system is preferred, The redox combinations of such a peroxide with S0,; and an oxidizable heavy metal ion, such as Fe++ or an N,N-dialkyl aniline are especially useful.

A preferred polymerization system uses from 24% to 75% by weight of all monomers (more preferably 40 to 75 17:5 to 70% of a solvent for the polymer and from O to 20% of a non-solvent for the polymer as a diluent in a continuous polymerization.

This invention permits the use of monomers in making copolymers of acrylonitrile containing sulfonic acid groups that have hitherto beenimpractical or too costly due to the low relative utilization of such monomers. The copolymers containing such sulfonic acid groups are especially useful in that strong fibers and films which are readily dyed with basic dyes to deep fast colors can be prepared.

The claimed invention:

1. In a-proces's for preparing a polymer of acrylonitrile which comprises polymerizing a monomer mixture containing at least by weight acrylonitrile based on the weight of total monomers and up to about 14% by weight of an ethylenically unsaturated monomer copolymerizable with acrylonitrile based on the weight of total monomers,

and between about 0.1% and about 3.0% of a mono ethylenically unsaturated sulfonic acid based on the weightof the total polymerization reaction mixture in a liquid medium, the improvement which comprises carrying out said process in the presence of a liquid mediumselected from the group consisting of a mixture of an organic solvent for said polymer selected from'the group consisting of dimethylformamide, dimethylacetamide, dimethylsulfoxidc, tetramethylene sulfone, butyrolactone, and ethylene carbonate and a diluent which is a nonsolvent for said polymer selected from the group consistingof water, benzene and methyl ethyl ketone, said mixture being so selected that the polymerization system has a dielectric constant of less than about 60 when measured at a temperature of 29 C.

2. The process of claim 1 in which the sulfonic'acid is in the form of an alkali-metal salt.

3. The process of claim 2 in which the alkali-metal salt is sodium.

4. The process of claim 1 in which the liquid medium is a mixture of water and dimethylformamide.

5.. The process of claim 4 in which the ratio of water to dimethylformamide is between about 40:60 and about solvent is present in an amount. from about 17.5% to 70% by weight of said polymerization reaction mixture,

and said diluent is present in an amount up to 20% b weight of said polymerization reaction mixture. j 9. The process of claim 8 wherein said monomer mix- Ohio (1956).

7 8 ture is present in an amount from about 40% to 75% by 1 2,796,414 Lowther et a1 June 18,.1957 weight of said polymerization reaction mixture. 7 2,900,370 Wilkinson Aug; 18, 1959 10. Thee-process of claim 8 wherein said process is a I continuous process. OTHER REFERENCES 5 Handbook of Chemistry and Physics 38th ed. pp. References Cited in the file ofthis patent v 329-2 1,. h 211 R P b h l' UNITED STATES PATENTS 2 33 C emic I ubber u lis mg Cro, C eveland 2,501,256 Bruson -4 June 24. 1952 

1. IN A PROCESS FOR PREPARING A POLYMER OF ACRYLONITRILE WHICH COMPRISES POLYMERIZING A MONOMER MIXTURE CONTAINING AT LEAST 85% BY WEIGHT ACRYLONITRILE BASED ON THE WEIGHT TO TOTAL MONOMERS AND UP TO ABOUT 14% BY WEIGHT OF AN ETHYLENICALLY UNSATURATED MONOMER COPOLYMERIZABLE WITH ACRYLONITRILE BASED ON THE WEIGHT OF TOTAL MONOMERS, AND BETWEEN ABOUT 0.1% AND ABOUT 3.0% OF A MONOETHYLENICALLY UNSATURATED SULFONIC ACID BASED ON THE WEIGHT OF THE TOTAL POLYMERIZATION REACTION MIXTURE IN A LIQUID MEDIUM, THE IMPROVEMENT WHICH COMPRISES CARRYING OUT SAID PROCESS IN THE PRESENCE OF A LIQUID MEDIUM SELECTED FROM THE GROUP CONSISTING OF A MIXTURE OF AN ORGANIC SOLVENT FOR SAID POLYMER SELECTED FROM THE GROUP CONSISTING OF DIMETHYLFORMAMIDE, DIMETHYLACETAMIDE, DIMETHYLSULFOXIDE, TETRAMETHYLENE FOLFONE, BUTYROLACTONE, AND ETHYLENE CARBONATE AND A DILUENT WHICH IS A NONSOLVENT FOR SAID POLYMER SELECTED FROM THE GROUP CONSISTING OF WATER, BENZENE AND METHYL ETHYL KETONE, SAID MIXTURE BEING SO SELECTED THAT THE POLYMERIZATION SYSTEM HAS A DIELECTRIC CONSTANT OF LESS THAN ABOUT 60 WHEN MEASURED AT A TEMPERATURE OF 29*C. 